That's AWFULLY tight. What if the line at immigration is long? What if the line at security is long? Assuming you can hop onto a N'EX or Skyliner the minute you come out of immigration, it's a 70-90 minute ride into Tokyo. And that's a big IF. Most likely you will have to wait 10-15 minutes for the next train. On both ends.

Also, even if some miracle allows you to make the trip there and back within the time frame, your ticket on the N'EX is clearly marked Narita (Terminal 1 or Terminal 2)-->Tokyo/Shinjuku, etc, and is for a specific seat on a specific run. When the conductor checks your ticket for the return trip (and he will), you're going to have the wrong one.

If the package doesn't have to be handed over personally, I'd just take it to the Takkyuubin counter and have them ship it. (That's what I do with heavy luggage when I have a long stay in Tokyo planned.)

If your package is extremely valuable or confidential or otherwise cannot be safely entrusted to another person, I would ask my friend or a trusted intermediary to come out to Narita and pick it up.